The disclosures herein relate generally to communication systems and more particularly to communication systems which compress text and other information for more efficient transmission to portable communication devices.
Intelligent mobile or portable devices such as personal digital assistances (PDA's), smart phones and small hand-held computers are becoming more common. To enable mail and other messages to be electronically delivered to mobile devices, the mobile device is typically connected to a mail server either through a wireless link or by a fixed wired connection when the device is cradled or docked. The fixed wire connection, such as via a docking cradle of an internet-connected desktop computing station, tends to be a relatively inexpensive way to connect a mobile or portable communication device to a distant mail server. In contrast, a wireless link tends to be a much more expensive way to connect a portable communication device to a distant mail server. This is so because the infrastructure required for wireless communication is more costly and more bandwidth limited than typical wire line infrastructure. To make more efficient use of available bandwidth, compression techniques are often employed.
It is useful to occasionally update the portable device with information from the mail server. For example, as time goes by the mail server will receive mail which is addressed to a particular portable device. The activity of updating the portable device's stored data with messages and data intended for a particular portable device may be referred to as synchronizing or synching the mobile device. A typical conventional communication system may include hundreds of portable devices each with its own mailbox on the mail server. Periodically the mail server can open all of the mailboxes and send newly arrived messages to the mobile devices.
In a mail or other data exchange between a conventional mail server and a portable device, the compression methods used typically analyze the data that needs to be transmitted by one device to the other, i.e. from the mail server to the portable device. Existing methods analyze the data to find the most frequently repeated patterns of text that appear in the data and encode them using fewer bytes while transmitting the patterns also as part of the data. In other words, the mail server sends a dictionary of the repeated patterns to the receiving portable device so that the receiving portable device will know how to decode the pattern on the other end.
What is needed is a way to achieve greater effective compression rates when transmitting data between two or more devices and a way to more efficiently use available bandwidth.